


What Big Teeth

by Daiako (Achrya)



Series: The Crow Clan [1]
Category: Haikyuu!!
Genre: Alpha/Beta/Omega Dynamics, Alternate Universe - Demon Hunters, Alternate Universe - Demons, Dubious Consent, M/M, Reunions, Somnophilia, Tail Sex
Language: English
Status: In-Progress
Published: 2018-04-08
Updated: 2018-04-09
Packaged: 2019-04-20 01:41:55
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,654
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14250354
Author URL: https://archiveofourown.org/users/Achrya/pseuds/Daiako
Summary: “You look a little lost, Omega.” His lost friend said, voice a low rasp that made Tadashi’s stomach flip. There was noise from the other demons, tittering and interested jeers, laughing echos of ‘omega’ that chilled him to his core. “You shouldn’t be this far from home.”The elders always said stay out of Crow Forest but Tadashi is nearly a fully grown hunter. He's sure he has it under control...until he doesn't.





	1. Chapter 1

**Author's Note:**

> This is a tumblr fill, for the starter 'You look a little lost, omega" and that gave me Little Red Riding Hood vibes which made me think RWBY/monster hunter (also hi, I like monsters) and so here we are. I have this whole story in my head where they’re still childhood friends, with dreams of being hunters but something goes wrong, as it does in such stories, Tsukki vanishes and then this. 
> 
> Which is too much backstory for what I meant to be two pages of porn, my god.

 

Tadashi will be willing to concede, at a later point when the world makes sense again, that all the warnings to stay out of the deep parts of the Crow Forest may have been more than just warnings meant to keep young hunters in line. He had always figured all the stories about monsters stronger than they could handle, of roaming shifter and demon packs beyond the borders of Miyagi that would tear them apart, were just…stories. 

After all how could anything be worse than the monsters who already slipped into their lands under the cover of darkness and threatened them? 

But now, surrounded by the glowing, slitted eyes of a half dozen demons, backed up against a tree by a monster wearing the face of a boy he’d considered his best friend. A face of someone who was supposed to be long dead, torn to shreds and left an unidentifiable lump on the border of Crow Forest along with the rest of his unit, a cautionary tale for all young hunters. It had been years, six to be exact, and Tadashi had spent every single one feeling like he was standing on the edge of something, breath frozen in his chest painfully, unable to let it go or breath in deeper. 

Forever choking, strangling, on the lack of Tsukishima at his side. Weighed down by all the what ifs, and his anger at the unfairness of everything that happened. Tadashi, who had no natural talent and was far from on the same physical level as those around them, got to live and push forward in his training, and Tsukishima with all his potential had been snuffed out at the far too early age of fifteen. 

“Tsukki?” His voice shook on the word, cracked then faded into nothingness, swallowed up by the still darkness of the forest. 

If not for the red tinged moon above them, peeking down at the scene playing out through the thin, skeletal branches of the trees surrounding them, he wouldn’t be able to see at all. The shadows seemed to have a life all their own, nipping at the edges of the small clearing they were in, twisting and turning in ways that didn’t seem to obey any light source. And then there were the lamp bright eyes of the other demons as they watched them.  

Tsukishima lifted his chin, lips pulling into a familiar whisper of a smirk. The hand he was using to pin Tadashi’s above his head tightened its grip; claws dug into his skin, easily puncturing the leather of his archery glove and guard.  He breathed in, scenting the air, and his eyes gleamed a cold gold. 

“You look a little lost,  _Omega_.” His lost friend said, voice a low rasp that made Tadashi’s stomach flip. There was noise from the other demons, tittering and interested jeers, laughing echos of ‘omega’ that chilled him to his core. “You shouldn’t be this far from home.” 

He leaned closer, bending down to bring them nose to nose. “Did you come looking for something?”

The truth was he’d come out hunting. It was his last task before becoming a full fledged hunter, to take down a monster alone. They were supposed to stay close to the border, pick off one of the roamers who crossed into Miyagi, but Tadashi hadn’t wanted to wait and compete against those with more skill so he’d ventured into the forest. He wasn’t sure when, exactly, he’d lost the path and gotten turned around but he’d found himself hopelessly lost in the dense forest, compass unable to find north and the terrain so unfamiliar there was no chance of catching the sight of something familiar. 

And then the demons. They’d come melting out of the darkness and sent him running. He’d been able to tell right away they were corralling him, cornering him, jumping out to bat away his weapons and claw at his clothes before fading back into the dark to laugh and taunt. And then…Tsukki. 

“You’re dead. They said…you…I don’t.” He stopped, throat so tight it was hard to force the words out, and searched the familiar face for any hint of recognition. Tsukishima just stared at him, the picture of boredom. “Why didn’t you come back?” 

Tsukishima touched his neck, the clawed tips of his fingers dragging along his jugular, scratching along his skin. There was a flash of pain, a line of heat, and then the demon’s hand was curling around his neck, pressing down on his throat. It wasn’t enough to cut off his air but it was enough to feel the tightness of it when he swallowed. He crowded even closer, the lean line of his body pressing against Tadashi’s from knee to chest. 

They stared at each other, breath mingling and eyes locked. Tadashi wanted to shrink away, to *look* away but he couldn’t, trapped by hypnotic gold. And, he realized, by the scent of him. It was different, sharper, eartheir, stronger than he remembered, layered in sweat and something heady and distinctly alpha, but also familiar. It reminded him of long hours spent sparring, studying in the library shoulder to shoulder, long summer days spent sneaking around in the orchards and fingertips brushing beneath tables. 

Of promises made, naive and wholeheartedly. 

Tadashi blinked in a futile attempt to hold back tears. He strained against the iron grip around his wrists and tried to shake his head. “Tsukki, please.” 

“…were you planning to share or..?” Someone asked, shattering the silence. Tadashi jumped, eyes darting to the side to find another demon, tall and lanky with hazel cat-eyes, wild dark hair, sharp features, and needle sharp fangs. “We did chase him down for you.” 

There were some murmurs of agreement. Tadashi pushed himself flatter against the tree, booted feet scrambling against the slick underbrush, fear settling in his chest. Share him? Did they mean to…he could think of a few things and, honestly, among the things that flashed through his head being killed and eaten seemed like the least painful. 

Tsukishima scoffed, eyes rolling. “Shut up. …I’m keeping him.”

“What?” Tadashi asked, alarm spiking. He got his answer a moment later, when Tsukishima forced his chin back, exposing more of his neck and shifted towards it. “No! Don’t!” 

“No?” Was breathed against his neck, inhumanly hot and damp. “Isn’t this what you want? You promised to be mine, didn’t you?” 

He jerked in surprise-he remembered that? Remembered him and his earnest insistence that one day, when they were old enough, they would be hunter partners and mates- and in that moment of shocked memory teeth bit into his neck. There was a flash of pain as his skin gave way then a dizzying wave of heat and…aching pleasure. It hit fast, spread out through his body from that point in a rush of tingles and warmth. He imagined champagne bubbles, tiny and fizzing as they burst under his skin. 

His head spun and the world darkened around the edges as his body went limp, all the tension in his muscles draining away like someone had pulled a plug inside of him. 

He felt…hot. 

Tsukishima’s released the bite and licked at his throat, tongue laving over the tingling flesh. Tadashi moaned and shuddered, head lulling to the side. 

“Don’t half ass it, four eyes.” Came from somewhere far away, echoed strangely in Tadashi’s ears. 

“Wha-” He slurred out, tongue thick and clumsy in his mouth. The world tilted and he moved, was spun around to face the tree then had his hands pinned back to the trunk before he could think to protest. 

Tsukishima nuzzled behind his ear as his free hand nimbly undid Tadashi’s belt and the laces of his pants. They slipped down to tangle around his knees, leaving him bared to the humid night art and the scorching heat of Tsukishima behind him. A hand skimmed the curve of his backside, cupped and squeezed before moving downwards to touch him elsewhere. He gasped, lifted up onto his knees as he felt himself being pressed into. 

It was a rough, uncomfortable drag at first, burned faintly but then it was slick, easier. Better. Sharp teeth and a greedy mouth bit and sucked at his neck and throat as his body opened up wider around more questing fingers. His thoughts were tumbling around, half formed and too hard to grasp onto, and his head was heavy, pounding, foggy. He was making sounds he couldn’t help, thrills and whines dragged from deep in his throat that barely sounded like him. 

He had a fleeting thought of ‘Not like this’ but it burned away, settled on his tongue like bitter ashes. Tuskishima pushed even closer, fit Tadashi into the cradle of his hips and then-

“Ah!” He yelped when something bigger, hotter, more, pressed deep into him with a single, hard thrust to the root. It was…he was. The world spun and melted, becoming nothing but heat and pressure and “ _ahahTsukkiplease_.” A steady press and slide, Tsukishima filling him deeper than he’d ever thought possible with forceful thrusts. He was draped over him, boxing him in and taking taking taking. One of his legs was lifted up, bent, changing the angle and he sobbed and thrashed. It was too much, ached so good. 

It was rough and filthy, hurt in a way that was so good he hadn’t thought it possible. Pleasure simmered in him, spilled out sticky and thick to trickle down his thighs and he rocked back, climbed higher and higher as the world spin faster and faster. He was…it was-he couldn't- 

Was he melting? 

With a hard snap of his hips Tuskki’s knot forced its way into his body, throbbing and thick, swelling bigger in his slick passage. Tadashi shouted, world going dark, and lost himself as his body convulsed and spent itself against the bark of the tree.    

His hands were released, allowed to slide down the rough bark of the tree, and a moment later fingers pressed against his mouth, past his lips. The taste of copper spread over his tongue. 


	2. Chapter 2

**Summary for the Chapter:**

> Tsukishima knows now he's spent the past six years hungry.

**Notes for the Chapter:**

> Vaguely alluded to Tsukki/unnamed others. The Crow (and Cat) Pack is decidedly poly so he's been around. It's fine. That's how demons roll, though Tsukki seems to be of a mind to become a one omega sort of demon now. 
> 
> Somnophilia and tail sex.

_ Yamaguchi dropped onto the bench next to him, body radiating heat and face dripping sweat. There was a bruise starting to form high on his cheek but he was smiling, pleased with the progress he’d shown in his sparring match against Hinata. Kei didn’t smile back but he also didn’t protest too much when the brunette leaned against him, sweat soaked body fitting against his side.  _

_ His scent was stronger after all that effort, simmered bright and sweet in the summer air, and heat bubbled to life low in Kei’s gut. Yamaguchi had presented recently and things had...changed. Kei had already resolved to not care what his friend presented as, was ready to accept him as an alpha or beta or omega. He’d already decided long ago that they would be partners and there had been long looks and quick kisses exchanged; dynamics wouldn’t change anything.  _

_ But it had changed things. Something had come to life in Kei, an ever present hunger that only being close to Yamaguchi could start to satisfy, and with it a tight, possessive thing that burned in him whenever anyone else came near the omega. It made him want to lash out, to snatch him up and carry him away, to hide him in a place only he could get to. It wasn’t something Kei would ever give in to but it was there. Always there. Burning.  _

Mine _ , it whispered as it prickled in his blood,  _ mineminemine.

_ He wanted Yamaguchi more than he’d ever wanted anything in his entire life. He thought, sometimes, that he could starve and dehydrate, die slowly and in pain, and it would be fine if Yamaguchi was with him. Absurd. Stupid. So foolish that it made him hate himself, was he really some starry eyed alpha drooling behind an omega, but he couldn’t help it. No amount of talking himself through it or trying to suppress it did a thing about the hunger gnawing at him.  _

_ He wanted him. He had, already, but now it was stronger, undeniable, a sharp pain in his chest when they were apart and an itching in his gums when anyone else looked Yamaguchi’s way. _

_ Yamaguchi’s hand brushed against his own, lingered, and then the omega pulled away to straighten up. His face was pinker and his smile wider. “C’mon, I brought lunch for both of us.”  _

_ Something pulled in Kei’s chest.  _

\----

Tsukishima wasn’t surprised that Yamaguchi passed out after the initial claiming. Humans weren’t the most hardy of creatures to begin with and Yamaguchi had been chased down, confronted with information some might consider mentally taxing, claimed and mated...vigorously. It was a lot to deal with. Tsukishima didn’t mind having to carry the unconscious omega, and waved off Azumane’s offer to do so. 

The other alpha was bigger, stronger, and logically would have been a better choice but Tsukishima had declined. Their dens weren’t too far from where they’d managed to corral Yamaguchi to and the human wasn’t that heavy, not to a demon. But even if he had been Tsukishima wouldn’t have let someone else hold the omega. The idea set his teeth on edge and made his skin itch. 

A silly thing. No one in the pack would try to take Yamaguchi from him, most had their own mates and were very comfortable with sharing so they weren’t exactly lacking in options. They had no need of his easily worn out and broken, unturned (for now) human.They weren’t a threat and yet...yet. He'd been like this before, as a human, possessive and on edge but it had been more controllable then. He’d been able to let others get close to Yamaguchi, for training and day to day things, with little more than a frown but now…

He doubted he could do that now. 

He held Yamaguchi as close as he could, doing his best to keep the human steady and not jostle him too much on the trek to the dens. He was allowed to split off from the scouting group as soon as they crossed into Crow Pack territory to go to his own den, a small cottage built around the trunk of a partially hollowed out tree. There wasn’t much too it, a small table, draped with a cloth with candles set on top of it, and sitting cushions scattered around, a small wood burning stove, and shelves holding the few things he owned. The main support, the tree, held his sleeping area; layered with cushions, furs, and thick quilts, sectioned off from the rest of the small area by a beaded curtain. 

He laid Yamaguchi down and, after settling a fire and placing water on the stove to heat, carefully stripped the omega from his clothes. Tsukishima stripped down as well then took the heated water and a rag to the hollow, intent on cleaning his omega of the sweat and fluids that had tried to his skin. Crouched next to him, in the soft glow of the fire, Tsukishima let himself look, really look, at the brunette for the first time in years.

The Yamaguchi dozing fitfully before him was different than the one who he’d left behind with the rest of his human life. The last six years had changed them both and if he'd ever considered seeing Yamaguchi again he would have expected that but...he hadn't ever considered it. The Yamaguchi in his head was forever fifteen, tall and lanky, messy haired, and a mix of sweetness and sharpness, of thoughtlessly adoring and willing to call him on his shit, of omega softness and quiet and something harder, stronger, just beginning to emerge. 

There wasn’t much softness to him now. He was hard and lean, with defined muscle in his arms, shoulders, back, and abs. Omegas, human and demon alike, tended to carry a bit of weight around their hips, stomachs, and chests but Yamaguchi had very little of that. His skin was sun browned, more freckled than he remembered, and there were scars where there hadn’t been any before, thin white lines and pockmarks of gnarled flesh here and there. His fingers were knobby and tilted in a way that suggested they’d been broken and set at least once in his life.  

His hair was long enough to be drawn up into a small ponytail though the clasp holding it up had been lost in the forest, allowing it to fan out over his face and over the pillow. His face had lost much of the roundness of childhood, now sharper and thinner. Tear tracks had dried over his cheeks and at the corner of his eyes. His lips were downturned, pale pink and the bottom one temptingly full, and parted as he slept. His neck, long and graceful, was flushed an angry red around his mating gland and the stark outline of Tsukishima’s teeth. Blood had dried to Yamaguchi’s skin in streaks; Tsukishima could still taste it, and the oily musk that came with piercing a mating gland, on his tongue. 

A thrill went through his body at the thought, at the memory of his teeth in Yamaguchi’s flesh, and went straight to his cock then settled low in his stomach. If he were still a human he would have been disgusted with himself but he wasn't and had long given up trying to cling to old impulses and morals. 

Tsukishima Kei had died, torn into by a rogue, mad demon who’d ventured into Miyagi territory during his team’s regular patrol, and everything he’d wanted or cared about had died with him. He’d buried that person, had needed to do in order to survive. 

Just being alive, saved by Daichi of the Crow Pack who’d come across the slaughter of his team while tracking the rogue demon, did not change anything. He’d been the only one of his team who hadn't been too far gone for the demon transformation to take hold and heal them, lucky that he'd been compatible with Daichi and hadn't gone past the point of no return. Lucky that Daichi had taken pity on a pitiful human left barely breathing, guts and blood spilling out of his body. Lucky...but. at the same time it had been a bitter sort of luck. He was changed, no longer human, couldn’t return home, and all there had been left for him to do was forget it all. 

Forget who he’d been and accept who he now was. 

He was even more changed than Yamaguchi was, the demon turning having done it’s work very well. Even taller than he’d already been, and while he wasn’t much broader he was more muscular, stronger, more durable than any human could hope to ever be. His pupils were stretched, narrow slits trapped in amber and gold irises, his eye teeth now long, razor sharp fangs, and his tongue long and rough. The nails on his hands and feet were black and sharp, claws that grew and retracted. He had gained a tail of sorts, long and as dark as his nails, constantly swaying behind him; it had taken time to deal with the addition, to learn to walk and move with it, but these days he had it very much under control. It was a fifth (or sometimes sixth and seventh) limb of sorts, sensitive and capable of various tasks. 

None of them particularly useful but sometimes they could be fun. 

Being a demon had brought instincts and a change in perception. A sympathy for the creatures he’d once trained to kill without ever questioning the why. He had...friends, he supposed (he had some thoughts on that but it wasn't like any of his packmates listened when he told them he didn't like them at all). Daichi had turned him, fed him his own blood when he could have left him to bleed out and go cold, taken him in, given him a place, accepted him and his odd human tendencies. Let him find himself among them, as one of them, monsters he would have once killed on sight. He mingled with the other packs, the Cats and the Wall and others, when they came through, had a few lovers though never anything serious. Nothing even close to how he'd felt now.

He'd been turned on plenty, liked the people he slept with, maybe even felt things for them, but he'd never felt hungry, not like he did when he looked at Yamaguchi.

Still he'd been content enough. 

Or he’d thought he was. As he skimmed a hand down Yamaguchi’s thigh, felt the soft lightly haired skin beneath his fingertips, he knew he hadn’t been nearly as at peace as he’d wanted to believe. He’d been hungry the entire time, had wanted and needed and longed, but hadn’t let himself acknowledge it. Not until he’d smelled Yamaguchi in the forest, standing out against every other scent out there.  

His hand slipped between the omega’s thighs to ease them apart. He told himself it was so he could clean up the slick and dried come that was now flaking away from his new mate’s skin but he found himself setting the rag aside and touching, skin to skin. 

The hunger burned, grew, took hold like it had in the forest. When he’d smelled Yamaguchi and forgot about everything except chasing the omega, claiming him, mounting him. Turning him, with his own blood, making Yamaguchi like him. He knew, distantly, that it hadn’t been right to do it, or at least that he’d gone about it all wrong. Except those were human thoughts, human concerns, echoes of his past. He wasn’t human anymore and demons...demons didn’t worry about how they claimed their mates. They just did. If an alpha scented out the right person and got them to come willingly then fine but if they had to be chases, worn down, and won then all the better. It was more satisfying that way. Made that primal part of himself hum in contentment. 

He touched Yamaguchi’s cock, smaller than his own and flacid, and wrapped his hand around it. The skin was soft, velvety, and thrumming with warmth. He swept his thumb up along the length and circled the head; he licked his lips. Hunger boiled and twisted in his gut as he let his eyes trail down Yamaguchi’s body, past his balls, to where his entrance was puffy and red, gaping slightly from use. He thumbed at the pucker, working Yamaguchi open more, and a trickle of cloudy white fluid slipped free, ran over his thumb.

Tsukishima’s cock twitched and his tail whipped back and forth behind him. He nudged his thumb deeper into the omega, eyes darting up when the omega sighed breathily to find him still very much asleep but starting to go red in the cheeks. He pushed his thumb in deeper, a shiver racing up his spine as slick warmth pressed in around the digit. He pumped his thumb in and out, tongue trailing over his lips again as he watched the swollen pucker stretch and soften, exposing the soft pink of his insides. He went slowly, gently, not wanting to disturb his mate, stopping when Yamaguchi’s voice got louder or his expression creased too much, working two of his fingers into the omega’s slick, grasping heat.  

He didn't want to wake him, not yet. There was no hurry, not like in the forest when the need to be inside of Yamaguchi had been overwhelming to the point of blocking out the rest of the world. He could wait a bit, make sure to be careful like he hadn’t been before. 

He could do more, really claim the omega with every part of himself, rub his scent into tanned skin, leave impressions of his teeth on every inch of Yamaguchi, and fill the fragile human body with his seed over and over, until he was so full of Tsukishima he was ready to burst.  He could make Yamaguchi his on more than just a surface level, a proper claiming and mating. 

That sort of thing took time and it would be easier if Yamaguchi wasn't awake to try to get away or demand answers from him. 

It didn’t take long for Yamaguchi to begin to harden in his hand and for fluid to start to bead at the tip of his cock. It was tempting, so tempting, to taste him; Tsukishima’s mouth watered. He lowered his head and flicked his tongue out, gathering the taste of bitter salt and swallowing it down. He lapped at the head, pressed the flat of his tongue against it and swirled, and spread his fingers apart to make space. 

His tail was like his legs or arms. He didn't have to think about moving it, anymore than he did his other limbs. He just wanted it to happen, to grasp things or touch them, and it did. No different than when he wanted to cross a room or pick up his sword. When it came forward, snaked around his body and went straight for where his fingers were working, he it was an act of desire, of want, more than a conscious choice. 

The tail shivered then the smooth skin at the tip split, which he felt as an itching sensation rather than pain, to allow the slick blunt head of what laid beneath to slip free. That to just happened, a rippling and shifting under his skin, brought on by arousal and want. Another ripple and his tail split along the length, becoming two instead of one. Tsukishima wasn't a shapeshifter, not a proper one like Daichi was, but he had some traits inherited from his maker. Traits he, admittedly, mostly used for sex. 

It was probably not the best use of his ability (it did not meet with Daichi’s approval) but he’d never felt any urge to make it work in other ways, not seeing the point in it. It served him well enough as it was. 

He let the tip brush against Yamaguchi’s rim, gliding through the slick sliding down over his fingers, before pressing inside between his spread fingers. Tsukishima shivered as his tail entered Yamaguchi’s body, the tight wetness clenching then fluttering around him. His other tail wrapped around Yamaguchi’s cock, freeing up his hands to skim over trembling thighs down to Yamaguchi’s ass to lift the omega some and then spread his cheeks wider. His tail stroked up and squeezed, rotated as it coiled around the omega’s cock, stroking with firm, steady pulls. 

Watching his tail start to plunge into Yamaguchi, dark and shining with slick as it , was… Tsukishima felt lightheaded at the sight. Slick squished and dribbled with every thrust and Yamaguchi’s pucker stretched and his body clung to Tsukishima, vice tight in spite of his thorough preparation, seemed to try to pull him back in everytime he drew out. 

Yamaguchi’s scent was changing, dripping honey thick and sweet in the air around them, and the soft breathy moans he’d been making were deeper, headier, thrummed in Tsukishima’s ears. He felt it the same as he would if were his cock in the omega, the nerves in his tail that sensitive, and pleasure spread through him in waves. He lifted Yamaguchi a little higher, plunged his tail in deeper, faster, harder and-

“Ah!” Yamaguchi shuddered, arching up off of the blankets. Tsukishima’s eyes jumped up, locked with confused, glassy brown ones. He watched Yamaguchi’s lips tremble and part, his throat bob, and his pupils stretch wide. “What-” 

Tsukishima didn’t give him time to speak, dropping down to fit their mouths together and licking past parted lips. His tongue twisted, brushed over Yamaguchi’s, then slithered deeper to take and fill the human’s throat. 

Yamaguchi moaned, muffled and wet. 

**Notes for the Chapter:**

> Not sure where this is going just yet but...well. You guys were so nice and the response really floored me so I just...wanted to give you guys more. ...In the form of shape shifting tail dicks. :) (I recently read Hellcat, by Sadie Sins, and there was a lot of tail dicks and hair tentacles and I'm not gonna lie, I was inspired.) 
> 
> Anyway, I want to at least do another chapter, with Yamaguchi's pov of this tail dicking. And maybe a fourth, where we see the Crow Pack and who it consists of. And then...we'll see.

**Author's Note:**

> I kinda want to write more of this. I have this whole thing in my head about Tsukki's little demon pack/their existence out there and, idk, maybe some tentacle porn in the pipeline if that's of interest to anyone aside from me, lol.


End file.
